This invention relates to an adjusting base for geodetic instruments with a levelling upper part receiving the instrument.
Such known adjusting bases are either fixedly joined to the geodetic instrument or they have a receptacle for such instruments. German DE-OS No. 2 558 759 (Ertel-Werk) shows a surveying instrument with a levelling base in place of the usual tribrach. The levelling base may be put on a plane head of tripod. When the instrument upper part is tilted its annular spherical face glides on a corresponding face of a lower supporting plate.
German DE-AS No. 1 269 370 (Carl Zeiss) shows an adjusting base removable from an instrument. This base is carried by a head of tripod plate by means of supporting bolts. It may thus be centered on the plate while a rotation between base and plate is prevented by a guiding plate arranged between base and plate. This guiding plate has slots for guiding the supporting bolts and pins secured to the head of tripod plate. Swiss CH-PS No. 447 632 (Carl Zeiss) shows a ball socket base for surveying instruments likewise removable from the instrument. This base has a ball joint for coarse levelling and a tribrach for fine levelling. The tribrach is joined to a lower supporting plate in a torsion-proof way by means of a ring-shaped metal membrane. This ball socket base has a socket with a radial clamping screw provided in the tribrach for receiving a standard peg (DIN-standard 18719) of the surveying instrument to be levelled.
The ball socket base according to CH-PS No. 447 632 (Carl Zeiss) may only be used for receiving standard pegs of surveying instruments. Other levelling bases are known for use with other instruments. These bases, however, cannot receive standard pegs. Such a known levelling base for surveying instruments made by Wild-Heerbrugg, Switzerland, has an instrument receptacle carried by three adjusting screws resting on a supporting plate.The instrument receptacle has three bores to receive three pegs of an instrument. The three pegs are clamped to the receptacle by means of a ring with three blades turnable around the receptacle axis and a rotary drive gear.
An object of this invention is to provide an adjusting base for geodetic instruments, which is suitable for both instruments with a standard peg and other instruments.